1,3

Only even numbers yield primes hence odd numbers are not considered.

There is an upper bound: if n has only k different prime divisors > 2, then a(n) <= 2^k. - Matthias Engelhardt, Jan 05 2004

T. D. Noe, Table of n, a(n) for n=1..10000

M. Engelhardt, Number of Primes arising as Sum of a Factorization.

a(9) = 2 18 = 1*18, 1+18= 19 and 18 = 2*9, 2+9 = 11, two primes arise.

Cf. A091350.

Sequence in context: A164272 A164273 A106277 * A230205 A024713 A123530

Adjacent sequences: A088624 A088625 A088626 * A088628 A088629 A088630

nonn

Amarnath Murthy, Oct 19 2003

More terms from Matthias Engelhardt, Jan 05 2004

More terms from David Wasserman, Aug 15 2005

approved